code: def event_callback(event: Event):
      pass
  
file_path: fastapi/tests/test_sub_callbacks.py
imports: from typing import Optional
  from dirty_equals import IsDict
  from fastapi import APIRouter, FastAPI
  from fastapi.testclient import TestClient
  from pydantic import BaseModel, HttpUrl
label_desc: Use image node_id 2 for calling a global function with example usage: event_callback(event) without return types